Expression of hsp90 and cyclin D1 in human breast cancer.

The integral roles of heat shock proteins (hsps) in the cell cycle and in multistep processes leading to tumorigenesis have been implied. We examined the expression of hsp90alpha, hsp90beta and cyclin D1 in human breast cancer. Levels of mRNAs coding for hsp90alpha and cyclin D1 were significantly higher in cancer tissues than in non-cancer tissues. Moreover, there was a close relationship between the extent of the two mRNA levels, suggesting that increased expression of hsp90alpha, an isoform of the hsp90 family, is associated with the proliferation of human breast cancer. Hsp90beta was expressed in cancer cells, but not associated with cell proliferation.